My unit also seems to be a little slower page turns after the update (someone else mentioned this earlier). Also, when turning on/off wifi from within a book, there is a very long pause when returning to the book using the back button. Not a huge deal, but it is quite noticeable.

I noticed slower page turns immediately after updating. However later on when I was reading on the bus it seemed back to normal. I noticed the light in the bus was more direct and stronger. So this perceived slowdown may be due to surrounding light levels.